Obesity is a condition with many potential causes.
Gluttony can do it, even in the absence of sloth.
Sloth can do it, even in the absence of gluttony.
Ignorance alone can do it.
Being inclined toward sin is not the same thing as being "insane." (unless we are all insane)
Being deceived/ignorant is not the same thing as being "unintelligent." (unless we are all unintelligent)
People who try to say that obesity is all down to any one factor, or narrow set of factors, don't understand it any better than the people who try to claim that being fat isn't unhealthy.
Being fat is not good or healthy.
But to look at a fat person and decide that they must be fat because of whatever particular sin or defect you personally associate with fatness, and judge them as being guilty of (whatever specific thing) because they are fat...
Well, I strongly caution against making allowances for ourselves to indulge in judging the condition and state of another person's soul, or assuming we know their particulars,based on their outward appearances.
There is nothing wrong at all with dismissing fat people as potential spouses based on the fact that one is not attracted to fat people for the very sound reason that excess fat is problematic for both health and beauty.
Where people go wrong is when they take their very natural preference for optimal health/genetic quality for coupling and breeding purposes, and feel like they have to defend it by making fatness out to be an indication of WORSE SIN/GREATER MORAL FAILING than anything perpetuated by thin people.
Based on many replies in this thread, even a relatively thin layer of excess fat (most of you would probably be pretty surprised by how small/subtle a visual difference 20 pounds up from ideal actually makes when spread across my 5'4" frame, and probably would never notice the difference if you were someone who saw me walking around/running my errands on the daily) is "massively overweight" and an indication that the entire person is horribly defective, likely in some irreparable way.
On the whole, I highly doubt overweight people are any more severely steeped in sin, or less repentant, or more stupid, or more crazy, than thin people. The main difference is that the specific consequences of their various behaviors are highly visible to others.
(There are even some people who are very slothful or very gluttonous - bearing in mind that overeating is only one of the ways in which the sin of gluttony manifests - and still end up looking normal/healthy from the outside for various reasons.)
It is fine to not want to marry a fatty based on the limitations of what one finds attractive and practically suitable.
It is unwise, uncharitable, and at least as ugly as cankles, to project a greater measure of sin/brokenness/unrepentance onto others based on the fact that we find them physically unattractive.